Semiconductor die or chips are encapsulated in a semiconductor package for protection from damage by external stresses and to provide a system for carrying electrical signals to and from the chips. Many different types of semiconductor packages exist, including dual-in-line packages, pin grid array packages, tape-automated bonding (TAB) packages, multi-chip modules (MCMs), and power packages. One type of power packages is a radio frequency (RF) power package, which are typically used when a semiconductor device in the semiconductor chip dissipates a power greater than approximately ten watts and operates at a frequency greater than approximately one hundred MegaHertz (MHz). RF power packages often include an air gap inside for lower power loss and better RF performance.
Current high power RF semiconductor packages use ceramic insulators, which are often called “frames,” that are brazed or soldered to a metal source substrate. However, the ceramic insulators are expensive and have poor mechanical tolerances.
Another high power RF semiconductor package is described in U.S. Pat. No. 6,511,866, issued on Jan. 28, 2003 to Bregante et al., and uses a polymer insulator or polymer-based frame. However, this package has potential reliability problems due to an inherently weak polymer/metal interface between the frame and a nickel and/or gold-based surface of the substrate. The poor seal is due to difficulty in creating a mechanically robust and consistent epoxy joint between the frame and the metal source substrate. Additionally, this package also has a high potential for mechanical failure at this polymer/metal interface in view of the new lead-free and other Restriction of Hazardous Substances Directive (RoHS) requirements that are being forced on the industry. Furthermore, this packaging also has potentially poor mechanical integrity under final mounting conditions.
Yet another high power RF semiconductor package is described in U.S. Pat. No. 6,867,367, issued on Mar. 15, 2005 to Zimmerman. However, this package uses a proprietary, high-temperature polymer material, which is molded to the metal source substrate before attaching the semiconductor chip to the substrate. Completing the package before the chip attach step creates mechanical reliability problems between the frame and the metal source substrate due to the high temperatures needed to attach or mount the semiconductor chip to the metal source substrate. Completing the package before the chip attach step may also limit the chip attach options. For example, if the polymer melts or degrades at four hundred degrees Celsius, then a gold silicon chip attach process occurring at over four hundred degrees Celsius cannot be used.
Accordingly, a need exists for a new high power RF semiconductor packaging that is less expensive than ceramic-based packages and that and has improved reliability over current polymer-based, air-cavity packages.
For simplicity and clarity of illustration, the drawing figures illustrate the general manner of construction, and descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the invention. Additionally, elements in the drawing figures are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of embodiments of the present invention. The same reference numerals in different figures denote the same elements.
The terms “first,” “second,” “third,” “fourth,” and the like in the description and in the claims, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms “comprise,” “include,” “have,” and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
The terms “left,” “right,” “front,” “back,” “top,” “bottom,” “over,” “under,” and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein. The term “coupled,” as used herein, is defined as directly or indirectly connected in an electrical, mechanical, chemical, or other manner.